Brake disk comprising a friction ring and a brake disk pot

ABSTRACT

The invention relates to a brake disk ( 2 ) comprising a friction ring ( 4 ) and a brake disk hub ( 6 ). Both the friction ring ( 4 ) and the brake disk hub ( 6 ) are provided with a ring land ( 8, 10 ) which overlap in a concentric manner. The ring land ( 8, 10 ) encompass recesses ( 14, 16 ) through which a joining arrangement ( 12 ) is guided in the form of a connecting pin ( 20 ). Also provided is a support ring ( 18 ) which encloses the ring land ( 8 ) of the friction ring ( 4 ) in a sandwich-type manner along with the ring land ( 10 ) of the brake disk hub ( 6 ). The support ring ( 18 ) comprises recesses ( 22 ) within which ends of the connecting pin ( 20 ) are supportingly mounted.

CROSS REFERENCE TO RELATED APPLICATION

This application is a national stage of PCT/EP2004/004657 filed May 3,2004 and based upon DE 103 21 796.7 filed May 14, 2003 under theInternational Convention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a brake disk.

2. Related Art of the Invention

Recently tribologically highly resistant materials are increasingly usedfor modern high performance brake disks. Here for examplemetal-matrix-composites (MMC) or carbon fiber reinforced ceramics on thebases of silicon carbide can be utilized. For car racing, friction ringsbased on carbon fiber reinforced carbon (C/C) are preferably utilized.Suchlike materials necessitate the usage of different materials for thefriction ring and the brake disk hub. Friction ring and brake disk hubtogether constitute the brake disk.

Various proposals have already been disclosed for the connection betweenfriction ring and brake disk hub. A commonly utilized connection betweenthe friction ring and the brake disk hub is a conventional screwconnection. An example for such a screw connection is disclosed in DE 9422 141 U1. Another form of connection between friction ring and brakedisk hub is the riveted joint, as disclosed in EP 872 659 A1.

Both aforementioned constructions have in common, that the friction ringas well as the brake disk hub feature ring lands, which are layeredabove each other concentrically, and are connected by a joiningarrangement. Usually bores are featured in the ring lands through whichthe joining arrangement passes. The disadvantage of this construction isthat during the transmission of the braking torque flexural stress isinduced into the ring land of the friction ring. Such a flexural stressmay cause fissures in the comparatively brittle ceramic friction ring.Therefore a huge design-engineering effort is necessary to preventfissuring in the friction ring.

SUMMARY OF THE INVENTION

The objective of the invention is to create a brake disk with a separatefriction ring and brake disk hub, in which the stresses which act uponthe friction ring through the joining arrangement are reduced incomparison to the state of the art.

The bake disk according to the invention features a friction ring and abrake disk hub. Here the term brake disk hub is understood as a linkingelement in general, which constitutes the connection between thefriction ring and the hub of the wheel. In the case that the frictionring is directly attached to the hub of the wheel, the wheel hub itselfis regarded as the brake disk hub according to the invention. Thefriction ring is understood as the part of the brake disk which contactsthe brake pads in a retarding engagement.

The brake disk hub as well as the friction ring features a concentricring land. Both ring lands feature a number of recesses. One joiningarrangement passes through each of the recesses of the ring lands of thefriction ring and the brake disk hub.

The invention is characterized by a support ring which is arranged suchthat it encloses the ring land of the friction ring together with thering land of the brake disk hub in the manner of a sandwich.Additionally, a connecting pin of the joining arrangement is arrangedsuch that it is supported in the recesses of the support ring whichcorrespond with the recesses of the ring lands of the brake disk hub andthe friction ring.

Thereby each joining arrangement running through the recesses of thering lands is supported by one recess of the support ring. The joiningarrangements are in this manner connected to each other. The support orbearing through the support ring prevents the individual joiningarrangement from inducing flexural stress onto the recesses of the ringland of the friction ring. Hence a revolving force acts onto each recessof the ring land of the friction ring from which a compression stressresults in the direction of load transmission. Particularly in ceramicparts a compression stress causes much less fissures than flexuralstress, which without the support ring according to the invention wouldact upon the ring land of the friction ring.

In one embodiment of the invention connecting pins are shrunk into therecesses of the support ring. Hence the connecting pins areperpendicular to the support ring and run through the recesses of thering lands of the friction ring and the brake disk hub, and are screwedtight on the side of the brake disk hub. For this a thread is providedon the connecting pin on one side of the brake disk hub. A nut sits onthis thread of the connecting pin and is tightened so that the supportring is pushed against the ring land of the friction ring.

In another embodiment of the invention the connecting pin features abolt head and on its other end a thread by which it is screwed into therecess of the support ring.

The recesses of the brake disk hub can be open radially towards theoutside. Thereby a radial expansion of the brake disk hub is madepossible. This radial expansion of the brake disk hub can also beallowed for by a recesses in the form of a slotted hole.

The present invention is particularly advantageous for a friction ringwhich consists of a fiber reinforced ceramic on the basis of siliconcarbide. Such friction rings exhibit a high tribological strength, areexceptionally temperature resistant and, in comparison to otherceramics, are very damage tolerant due to their fiber reinforcement.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous embodiments of the invention will be described in detailwith the illustrations below. They show:

FIG. 1 a perspective view of a brake disk with a friction ring, a brakedisk hub and a support ring,

FIG. 2 a cross sectional view through a brake disk with a brake diskhub, a friction ring and a support ring,

FIG. 3 a schematic illustration of the joining arrangement betweenfriction ring and brake disk hub with a support ring,

FIG. 4 a schematic illustration of a joining arrangement betweenfriction ring and brake disk hub with a support ring.

DETAILED DESCRIPTION OF THE INVENTION

The brake disk 2 shown in FIG. 1 includes a friction ring 4 and a brakedisk hub 6. The friction ring 4 in this embodiment is comprised of afiber reinforced silicon carbide ceramic.

The friction ring 4 as well as the brake disk hub 6 feature ring lands 8and 10. The ring lands 8 and 10 in turn feature recesses in the frictionring 14 and in the brake disk hub 16. These recesses 14 and 16 are shownin the cross sectional view of FIG. 2 and they are not visible in FIG.1.

In the brake disk 2 according to FIG. 1 there is also shown a supportring 18 which is arranged such that it encloses like a sandwich the ringland 8 of the friction ring 4 together with the ring land 10 of thebrake disk hub 6. Herein “like a sandwich” means that in an axialdirection first the ring land 10 of the brake disk hub 6 and then thering land 8 of the friction ring 4 and subsequently the support ring 18occur. The ring lands 8 and 10 and the support ring 18 feature recesses14, 16 and 22, which are arranged such that they form a continuous bore.

A joining arrangement 12 is routed through the recesses 14, 16 and 22(compare also FIG. 2). The joining arrangement 12 comprises of aconnecting pin 20 and a nut 24 (FIG. 2).

The ring land 8 of the friction ring 4 exhibits slots 34 in thecircumferential direction which point radially outwards and feature anend bore 36 on their outer end. The slots 34 are arranged such that theyare each located equidistant between the recesses 14 in the ring land 8of the friction ring 4. The slots 34 interrupt the ring land 8, which isadvantageous in the case of expansion caused by thermal stress. The endbores 36 serve the prevention of notch stress on the radial ends of theslots 34.

In FIGS. 3 and 4 two embodiments of joining arrangements 12 are shownschematically. In the brake disk arrangement shown in FIGS. 3 and 4 thedisk brake is not identical with the one shown in FIGS. 1 and 2.Nevertheless the same reference numbers are used for parts with similaror the same function. The embodiment in FIG. 3 features a friction ring4 and a brake disk hub 6. Both in turn feature an ring land 8respectively 10 which overlap each other. The ring lands 8 and 10feature recesses 14 and 16 wherein the recesses 16 in the brake disk hub4 are in the shape of a radial slot. This oblong recess 16 provides roomfor a radial expansion of the brake disk hub 6 at elevated temperatures,without inducing flexural stress in the friction ring 4.

It maybe useful to introduce a sliding block (not shown here) betweenthe connecting pin 20 and the recess 16 which provides for a radialexpansion between the joining arrangement 12 and the brake disk hub 6.

The connecting pin 20 in FIG. 3 is arranged such that it is shrunk intoa recess 22 of the support ring 18. The shrinking is usually done by aheat treatment of the support ring 18, in which the cold connecting pin20 is inserted, wherein said connecting pin 20 constitutes a frictionalconnection with the support ring 18 after it has cooled down.

The connecting pin 20 perpendicularly extends through the recess 22 ofthe support ring 18. The connecting pin 20 is guided through therecesses 14 and 16 of the ring lands 8 and 10. On the end opposing thesupport ring 18 the connecting pin 20 features a thread 26. A nut 24sits on this thread 26.

The nut 24 is tightened against the ring land 10 of the brake disk hub 6whereby the support ring 18 is compressed against the ring land 8 of thefriction ring 4. The frictional connection between support ring 18 andconnecting pin 20 is sufficient to counteract a screw torque and toconstitute a frictional connection between the ring lands 8 and 10 andherewith between the friction ring 4 and the brake disk hub 6.

An axial clearance between the friction ring 4 and the brake disk hub 6may be necessary to provide for thermal expansion in the axialdirection. For this, a resilient element may be utilized which is notshown in FIG. 3. Such a resilient element may be constituted by a diskspring washer between friction ring 4 and nut 24. Further, it ispossible to ensure a resilient effect through an (also not shown)intermediate element between the connecting pin 20 and the recess 16.

Another schematic illustration of the joining arrangement 12 is shown inFIG. 4. Here the connecting pin 20 features a bolt head 32 on one of itsends. On its other end the connecting pin 20 features a thread 28. Inthis embodiment the connecting pin 20 is not shrunk into the supportring 18, but it is screwed in. Other than that, the embodiment shown inFIG. 4 is equivalent to FIG. 3.

FIG. 1 through 4 show preferred embodiments, in which the joiningarrangements are constituted by a screw or threaded connection.Fundamentally the advantageous effects of the support ring can beachieved through other joining arrangements. Therein e.g. a rivetedconnection or a combination of riveted connection and frictionalconnection, such as shrink fitting, can be utilized. It is alsoconceivable to use material connecting or adhesive bonds, e.g. weldingor brazing.

1. A brake disk (2) with at least one friction ring (4) which isconnected to a brake disk hub (6) by means of a joining arrangement (12)in which the friction ring (4) and the brake disk hub (6) each feature aconcentric ring land (8, 10) and the ring lands (8, 10) of the frictionring (4) and the brake disk hub (6) overlap, wherein the elements of thejoining arrangement (12) pass through recesses (14, 16) in the ringlands (8, 10), said brake disk further comprising a support ring (18)such that the ring land (8) of the friction ring (4) is located betweenthe support ring (18) and the ring land (10) of the brake disk hub (6),wherein the ring lands (8, 10) are connected by means of connecting pins(20) which are fixed in the recesses (22) of the support ring (18).
 2. Abrake disk according to claim 1 wherein the connecting pins (20) areshrunk into the recesses (22) in the support ring (18).
 3. A brake diskaccording to claim 1 wherein the connecting pins (20) feature a thread(26) on one side of the brake disk hub (6) and are fastened with a nut(24).
 4. A brake disk according to claim 1 wherein the connecting pin(20) is bolted into the support ring (18).
 5. A brake disk according toclaim 1 wherein the recesses (16) in the brake disk hub (6) are openopened radially outwards towards the outside.
 6. A brake disk accordingto claim 1 wherein the friction ring (4) consists of a fiber reinforcedceramic on the bases of silicon carbide.